With the conclusion of the Paris climate conference in December, global warming went from being the kind of problem politicians like to being the kind of problem they hate.

For at least the past year, the conversation about climate change centred on what kind of agreement Paris would produce. And so politicians got to posture, to say quotable things, to appear world-leaderish. As the talks were about to begin, for instance, Australia’s environment minister, Greg Hunt, said it was his “deepest hope and belief” that the world would reach a strong agreement, adding that it was “a deeply personal goal and commitment, as well as a national objective”. During the talks, he revealed that he, and Australia, was acting as a “broker” to make sure that the push by island nations to limit warming to an increase of 1.5 degrees Celsius would at least be “referenced” in the final accord. “Clearly [it] won’t end up as a formal goal of the text,” he said, since some nations would veto it, but he was “trying to be constructive by providing a pathway” so it could be mentioned.

And indeed he, or someone, was successful in the effort, for the final text, solemnised by all the leading politicians of the planet, including those from Australia, pledges them to “holding the increase in the global average temperature to well below 2 °C above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5 °C above pre-industrial levels, recognising that this would significantly reduce the risks and impacts of climate change”.

That’s a remarkable sentence. It lays out in no uncertain terms the most ambitious project the world has ever embarked on. The US secretary of state, John Kerry, called it “a victory for all of the planet and for future generations”. India’s environment minister termed it “a new chapter of hope in the lives of 7 billion people”. Not to be outdone, a beaming Mr Hunt pronounced it “arguably the most important environmental agreement ever”. Champagne corks were popped, backs were pounded, the Eiffel Tower was specially lit.

And then it was the next day.

Say you really are going to hold the temperature rise of the planet to 2 °C. We know with some precision what you’d have to do. A study published in Nature about a year ago, led by Christophe McGlade of University College London, looked at all the world’s fossil-fuel reserves, and found that most of them would need to stay in the ground. You couldn’t, for instance, drill for any oil or gas in the Arctic – those reserves would have to stay untouched. Countries like Australia and the US would need to leave around 90% of their coal reserves underground.

Oh, and say you were going to try and meet a 1.5 °C target. In that case you’d have to stop mining coal tomorrow.

This is not ideology. This is not propaganda. This is math, chemistry and physics. No one has challenged the numbers, because the numbers line up with science the world over. And the science lines up with … the relentless rise in temperatures. The steady melt of glaciers. The rapid acidification of the planet’s oceans. The rise in extreme weather, so that bushfire seasons everywhere now stretch almost around the calendar. The steady increase in atmospheric moisture, which means more drought in dry areas and more floods in wet ones. As if to demonstrate the seriousness of their pledge, the planet put on a little show for world leaders in the weeks after Paris: crazy record flooding from Paraguay to the Mississippi to the UK to Scandinavia; crazy heat from New England to South Australia; crazy drought in much of Africa, where millions are now going hungrier than they should. So the numbers are not just numbers; they are already having serious impacts globally.

More serious, it appears, than the politicians. In the US, within days of the Paris conference concluding, Congress gave a gift to the oil industry, lifting a 40-year-old ban on exports. Canada wants to go ahead with some new pipelines out of the tar sands, even though that Nature study makes it clear you can’t expand production of that filthy oil. And in Australia, it was literally 48 hours after the Paris accords that a Queensland court rejected an appeal by environmentalists to stop a mammoth new coal project in the Galilee Basin.

You can’t have both the Paris climate agreement and Adani’s Carmichael coalmine. Full stop. In fact, to have any hope of keeping to an increase of 2 degrees – much less 1.5 – you can’t have any new mines in Australia. Coal, at best, can continue its decline, tailing away to a minor industry over the next decades. But that’s it. And anyone who looks at the numbers knows it. The same goes for new offshore oil drilling, or new coal seam gas fields. Keep doing this stuff and the math doesn’t work.

So what’s going on?

One possibility is that Australia’s leaders are completely clueless, that they really haven’t made the connection between digging up the continent’s huge coal reserves and the heating of the planet. This seems unlikely. Malcolm Turnbull has known about climate change for nearly as long as Al Gore.

Another possibility is that they’re complete hypocrites – that they know they’re saying one thing and doing another, and that it doesn’t bother them because they’re bought off, or too scared of the climate sceptics in their parliamentary rump. Clearly this is true of some politicians, but not all.

The third, and most charitable, possibility is that they’re caught in a classic Augustinian trap. In his Confessions, the great philosopher and theologian Augustine recounts his early prayer: “Oh Lord, make me chaste – but not yet.”

We’re trapped in that moment when the past – coal – still has real purchase on the present. The money it generates remains important to the economy. The jobs it produces, though greatly shrinking in number, remain crucial to those who hold them, and the communities in which they live. If you were starting fresh you wouldn’t build coalmines and power plants, but you’re not starting fresh. Those things are already there – paid for and productive.

And the trap is not just economic; it’s even more psychological. For everyone involved, the easiest path would be to just let the current arrangements keep going. Inertia is an enormously strong force. Politicians, for instance, are comfortable with their current sources of support, both financial and electoral: by definition that’s who brought them to power. They can imagine a world a decade or two hence when the solar industry and the wind industry have acquired wealth and power, when they employ vast numbers of people, when they are the status quo. At which point the politicians will be happy to serve them. But they’re not there yet.

So the politicians hope they’ll get more time. Greg Hunt, he of the “deepest hope and belief” and the “deeply personal goal and commitment” and “arguably the most important environmental commitment ever”, had, in October, approved ongoing plans for the Carmichael mine, provided some changes were made to protect the southern black-throated finch. “The conditions I have imposed take into account issues raised by the community and ensure that the proponent must meet the highest environmental standards,” he explained at the time.

But those standards – the product of an earlier era when habitat for the black-throated finch was all we had to worry about – don’t work anymore. The job of politicians, if they aspire to be leaders, is to change those standards, and quickly – to make the future happen more quickly than it otherwise would, fast enough to get us out of the hole we’re caught in. Augustine kept his mistress for a decade after his famous words, which still left him plenty of lifetime to become a saint. But with climate change we’re now out of decades.

Bill McKibben is an author and the founder of the environmental organisation 350.org. His books include The End of Nature, Eaarth and Oil and Honey.

With the conclusion of the Paris climate conference in December, global warming went from being the kind of problem politicians like to being the kind of problem they hate.

For at least the past year, the conversation about climate change centred on what kind of agreement Paris would produce. And so politicians got to posture, to say quotable things, to appear world-leaderish. As the talks were about to begin, for instance, Australia’s environment minister, Greg Hunt, said it was his “deepest hope and belief” that the world would reach a strong agreement, adding that it was “a deeply personal goal and commitment, as well as a national objective”. During the talks, he revealed that he, and Australia, was acting as a “broker” to make sure that the push by island nations to limit warming to an increase of 1.5 degrees Celsius would at least be “referenced” in the final accord...